Electrical and optical properties of metal‐sandwiched ZnO/Ti/Cu/Ti/ZnO transparent conductive thin film

Abstract

Metal-sandwiched zinc oxide (ZnO)/titanium (Ti)/copper (Cu)/Ti/ZnO thin film systems were fabricated using magnetron sputtering technology and then annealed using a rapid thermal annealing system at temperatures from 100 to 400°C. The influence of the Ti film thicknesses and annealing temperatures on the surface morphologies, sheet resistance and optical properties were studied. The surface morphologies change a little with the annealing temperature rises. The sheet resistances reduce with the Ti film thickness or annealing temperature increasing. Both the max transmittance and figure of merit reduce with the increase of Ti film thickness. The max transmittance increases with the temperature increasing from 100 to 300°C and then reduces. However, the figure of merit increases with the temperature increasing which indicates that the metal-sandwiched ZnO/Ti/Cu/Ti/ZnO thin film system annealed at 400°C has the optimal performance.

Influence of Annealing Temperature on Optical Properties of Sandwiched ZnO/Metal/ZnO Transparent Conductive Thin Films

“…In particular, the bandgap of ZnO(Cu) thin film increases with temperature, while that of ZnO(Ti/Cu) first increases and then decreases. The increase of bandgap after annealing is caused by the Burstein-Moss migration effect [33], which is related to the increase of carrier concentration in the film (Figure 4). The increased carriers fill in the lower energy level of the conduction band, making the valance electrons transfer to the higher energy level, thus increasing the bandgap width.…”